This invention relates to the field of printed antennas and more particularly to the field of printed array antennas.
Printed circuit antennas are utilized at high microwave frequencies such as the Ku-band to provide compact light weight antennas. Planar printed array antennas are known in which a plurality of dipole antennas are distributed in a rectangular array on a substrate and fed through a feed network which provides equal amplitude and phase signals to each of the dipole antennas. U.S. Pat. No. 3,587,110 to Woodward which is assigned to the present assignee is an example of such an antenna structure and is incorporated herein by reference. Such antennas are also known which incorporate phase shifters within the feed network. U.S. Pat. No. 3,887,925 to Ranghelli et al. is an example of such a structure.
U.S. Pat. No. 3,474,114 to Shyhalla discloses a planar array dipole antenna having equal phase and amplitude drive signals in which the feed network is disposed on one side of a substrate and the individual dipole antennas are disposed on the other side of the substrate. This antenna includes separate feed connections for the two (left and right) halves of the antenna.
A need has developed for a flat printed circuit dipole array antenna which operates in a monopulse mode. Unfortunately, the existing printed dipole array antennas in order to operate in a monopulse mode require the addition of sum and difference circuitry off the substrate. Provision of such off-substrate sum and difference circuitry destroys the planar nature of the antenna and may significantly increase weight depending on the type used.
Thus, a printed monopulse array antenna is needed which includes sum and difference circuitry on the printed substrate.